Muffle tunnel kiln



Feb. 26 1924.

T. LARssoN MUFFLE TUNNEL KILN 2 Sheets-Shea? 1' Original Filed Jan. 28. 1921 INVENTOR fi ia 9 A ra-Mm Patented l' ebtzfi, 192

stars TEURE LARSSON, OF WOROETER,

MASSACHUSETTS, ASSIGNOR TO NORTON COMPANY,

MUFFLE TUNNEL KILN.

Application filed January 28, 1921, Serial No. 440,610. Renewed January 7, 1924.

T 0 all whom it may concern:

Be it known that I, Tnonn Lausson, a citizen of the United States of America, residing at Worcester, in the county of Worcester and State of Massachusetts, have invented certain new and useful Improvements in Muffle Tunnel Kilns, of which the following is a full, clear, and exact specification.

My invention relates to an improvement in the construction of'tunnel kilns and more particularly to one of the muffle type having a combustion chamber disposed longitudinally of the kiln.

Mutlie tunnel kilns, such as are commonly employed for high temperature work, have consisted of a longitudinal chamber through which ware-conveying cars may pass and combustion chambers on either side which supply the heat to the ware being treated. They have been built for the burning of solid, liquid or gaseous fuel, and with various arrangements for carrying off the gaseous products of combustion longitudinally or transversely through dues in the kiln wall without coming into contact with the ware which is being fired.

' Such kilns. as heretofore constructed, have the disadvantage that the heat radiating from the rear of the mufiie is not properly directed to the ware for efficient utilization, and that no adequate provision has heretofore been made for regulating the temperature conditions within the cooling zone of the kiln or. for giving the ware a uniform or desired heattreatment. In one type of kiln, the combustion chamber has double walls providing air ductswhich communicats with passages Within the car body and with the kiln chamber for the circulation of air therethrough, but such circulation must depend upon differences in density of the air caused by differences of temperature. \Vhen the kiln is in operation this force will be inadequate to produce uniformity of heat conditionsand will tend to concentrate hot air in thetop of the kiln chamber. As a consequence, the were in diti'erent positions in the car may not be uniformly fired or the temperature may not he sufiiciently controlled in all portions of the kiln for the proper treatment of ware which requires careful firing. Hence, there may be varia tions in structure, quality and appearance,"

which it is very important to avoid in the manufacture of articles, such as grinding.

wheels, which must be carefully inspected and tested before use.

It is accordingly an object of my invention to overcome such disadvantages and to heat a tunnel kiln chamber more uniformly than is possible with such prior constructions and generally to render the tunnel kiln operation more efiicient by utilizing heat heretofore wasted through the walls of the kiln or drawn oil from the mutlle chamber and to provide a kiln in which the temperature conditions may be readily regulated in different portions thereof.

More specifically, it is an object of this invention to utilize the heat which radiates from the combustion chambers in a direction away from the ware by providing heat conducting air ducts passing in the rear of the combustion chambers and then adjacent the ware to conduct heat thereto.

It is a further object of this invention to circulate such heated air positively to heat the inner root wall of the kiln chamber and the car top to provide further direct transfor of heat to the ware'and more uniform conditions within the kiln.

Further objects of my invention are to efiectively and evenly cool the ware within the cooling zone of the kiln b a forced cir cul-ation ofair through a con uit surrounding the were and to utilize such portions of the circulating air as may be desired to support combustion of thegases within the muffle chamber.

With these and other objects'in view, as

will be apparent from the following disclosure, my invention resides in the combination oi parts set 'forth in the, specification and as covered by the claims appended hereto.

A specific embodiment of my invention is illustrated by the accompanying drawings in which:

Figure 1 is a horizontal cross section, partly broken away, showing the combustion chambers, the vertical heating conduitsand the kiln cars; I

Fig. 2 is a horizontal cross section through the top of the tunnel kiln; on the line 22 of Fig. 3, showing the transverse conduits;

Fig; 3 is a vertical section of the tunnel kiln, partly broken away, through the combustion chambers and the heating chamber along the line 3-3 of Fig. 1 looking in the I direction of the arx'ews, and showing hiizi cars in position on the tracks;

Fig. 4 is a cross section of the tunnel kiln along the line 4-4 of Fig. 1, showing a kiln car in the cooling zone; and

Fig. 5 is a cross sect-ion f the csmbustion zone of the tunnel kiln along the iine --55 of Fig. 1, showing a, kiln car in pesitien en the tracks, fans connected with the out et ends of ihe combnsision chambers and a connected to the outlet ends 0f the hot :LLiI conduiizs.

In eceorrience with my innvei'ybioze pimviiie a, tunnel kiln with a cembustien chemher disposed longitudinally of the heating zone, which radiates heat from its 55mm iiirecfly toward the and item anether side in an air comiuit which is adapted in circulate the heated air in eiioihei QOZiZiQfi of the kiln Where it may irzmsmitits heat he the were. Ii yrefembiy ssi design this hiih consiruction that the air conduit may 355mm :1 continuous passage whereby may be positively iimwn through the semehy a. an or other suitable mechanism. In the specific form iihlsireted, this heeteei siixis across fzhe tap of the kiln for heat downwardi and then thmugh passages in the kiln car mix eneeih the were confluit therefer ms have a substantially helical path SHIZOUZIuEHF' the spaee ihi'oiiggn which ihe ware travels, pitch 0i ihe helix being provided by an oblique arrangement f the conduit enemy 02' mi emes 05 me k111i chamber.

b11108 PZGVIOUS meizheds in sailing me were in the cooling Z6313 have been deficient, i propose furthermore i0 suhs'tehtieliy Sill" rsuhd the (rs-01mgv zone "with, en 2111 002mm; which has refractery welis a depte-ri sew duct heat from the tunnei him, and A prefeebiy uhihze a cohstructieh siimiei to that of the heaimg zohe wherein the mey he drawn progressively thrmigh cmiiimieus conceit around the was? peseege, ably irongh the refrsc miy 395 13] 0-: m sea itsei'i in order to assist in 2 ie't-mg fiche tempemiure H1 ine heaimg mine i desireci amounts of heate an: item the conduit to the combustion chamber at spaced points. Fin-iiiermer-e air may be drawn fram the Oll'iSiiiB 0f the chamber hoh the air conceit in either zone and into the cembustian chamber in the heating; 2am, in order 'ihac ihe aempemture cmiemens he mere fuily regaie'i'el.

In aa-ceoi'i'iaiice with ihe specific QEKOOdk sh tion waiis "s sash a i ihe hoiiy 0f the hiir to run freeiy along interruption. The outer. side Weiie i1 12, which are built upon the foumietien Wfliis 1 and joined at the top by the auaer reef Wall 13, are held tege'thei" by suitsbi'y spaced steel plates 14 and erase s 5. T0 insuiate the kiln, a layer 1.6 ()f su n eteriai of w heat conductivity, such (3'. ecemeceeus earth, is placed ever the "mp the reef Wall and simihir filling is placed in ioiigiizuaiinei spaces 17 within the same seugheui the iength ef'the kiln As she simple ai'mhgement for heating the kiln 1 previiie an inner roof wail persiiei m the outer moi wail 13 but spaced from i am each side of the kih"; chami her the him v-erzicai. 20 and 21 0f suitehie refrsciory material, which are spaced from enter hiin walls and vextend the iengnh the kiin. These verticalwaiis connect ihe i'oumietionvwells l with the refraciory inner P001 Wall 22, thus forming an inner beefing or Kiln chamber for the passage the kihi ems, as shewn', particularly in 1 This moi well is suitably sf refractory plates 01 i'RichS the outer side walis ll the lain in that portion 03% th which is is whstitute ihe 110$ Zane,

i ihem are constructed the 112- efmciei y WRHS 25 and 26 which t mer sides 02": the roof wall mp, es iiinssrateci, and m psr'iziziens 29 and 30 at the hetism, connect them Wiih the Walls of the heating 20 and E21 respeciiveiy, the members heiieg spaced between the veri'v chi sirengthen the consfii'uction.

Th zmsi partitions, thus censtructe i, 10mm gzitudmai mmhusiien or muffie chamber i2 side the heating chem- .ifhe from the mute? iiiifi while 11 and 12 to farm spaces the of coinhnseien chambers, and as showm vertical pa'ritions are previcied to farm separated conduits 36 for 'zbhe eircuiatien 0f heated-gases, viii be explained: The inner r0031 wail tied in and integral wiih the mixer 5.3

by (if speced pm'i-itiens 3? en pievide oiumht v of conduits 539 he JP 1 V 3 auction 01 the kiln parts such 1S Wei understood 0; ceramic i-rli engineers.

similar consi'miczicn be employed in ii I w znne sf kiln, except usiion chambers are omitted. S30 and 21 are sepa- CHiOl WfziiS i0 term a coming 11s. This genera-ii eensti'uetion is' ieei Wniis and 2% are spaced t the inner roof wall 22 in this zone,

' into the kiln chamber.

air space. As shown, vertical partitions'40 similar to partitions in the heating zone are provided to form vertical conduits 41 and 42 which open into conduits 43 above which are formed similar to conduits 39 by partitions 44.

In order to provide for a circulation of air through the conduits around the cooling and heating zones, I connect these together so as to form a continuous passage, or, as illustrated, several parallel passages adapted to convey the air in a multiple relationship. If it is desired to heat the car bottoms by this circulated air, I may employ the construction shown. In this case, each car 50, which may be otherwise constructed in the usual form, is provided with transverse passages which communicate with the vertical conduits. in the kiln walls. To this end, the refractory body 51'of the kiln car may be built to provide a plurality of separate transverse conduits 52 located closely beneath the top of the car, which is suitably constructed for supporting the ware. On each side of the car and above the openings to the conduits 52 is a longitudinal flange 53 equal to the length of the car body which forms a sand seal with the trough 49 on the kiln wall. A similar seal beneath the openings is formed;byz.the flange 54 on the car and'the sand'trou gh 55 on the kiln foundation-w,alls L: These seals insure a minimum'of leakage of air from the conduits It of course is understood that a sufiicient number of similar kiln cars is provided so that when'placed end to end they will extend throughout the length of the kiln.

In order that the car passages may communicate with the vertical conduits in the heating zone, the lower ends of the conduits 36 co'hnect with short horizontal flues 56 and 57, formed by thefoundation walls 1,

the vertical-partitions" 58 and the. horizontal partitions 529 and '30 respectively, which enter the heating chamber. In the cooling zone, the vertical conduits enter the heating chamber through the openings 60 win the side walls 20 and 21, at such points as to connect with the conduits 52 in the tops of the kiln cars when they are in position on the tracks. In order to form a continuous or substantially helical air passage of the various conduits and fines described, I may arrange any of the sets of passages obliquely. In the particular form. illustrated. I have shown the transverse passages in the'cars"so arranged that they connect each conduit 56 with the fourth conduit 57 beyond it and on the opposite side of the heating chamber, whereby air may pass helically through a set of four parallel passages.

If it is not desired to take air directly from the kiln chamber, the first. four vertical conduits 41 in the side wall 11 are not connected with the heating chamber but have entrance openings 61 at their lower ends, which communicate with the outside of, the kiln for the introduction of fresh air. At the diagonally opposite end of the tunnel kiln the last four vertical fiues 36, in the side wall, do not communicate with the heating chamber but are connected through the outlets 62 and the air duct 63 to an exhaust fan 64, whereby the air may be forced to circulate at a desired rate.

At suitable points along the outer sides of the kiln walls, I provide openings 65 which pass through the wall 1 and the partitions between the vertical conduits 36 into the combustion chambers. Burners 66, which may be water cooled to prevent them from being destroyed by the temperatures attained in the combustion chambers, are inserted through said openings 65 into the combustion chambers and are connected with suitable oil or gas fuel supply .pipes 67. Air in desired quantities may also be introduced into the combustion chambers through regulatable openings 68 (see Fig. 3) closed by removable and adjustable caps 69. For the introduction of air directly from the hot air conduits to the muflies, I may provide a set of suitably spaced conduits 71 (only one being shown, in Fig. 3) which pass from the transverse passageway 39 to a point outside the kiln, and a similar set of conduits 72 opening into the muflie chamber 34. A regulatable communication between conduits 71 and 72 may be established by means of suitable mechanism, such as the slide valve 73 having a groove 74 adapted to connect the conduits when the valve is in one posh tion and to be shut olf from such communication by a solid portion 75 of the slide which covers opening 71 when theslide is in a second position. In order toprovide for further variation in the temperature curve,

conduits 76 having movable caps 77 may be spaced at desired intervals for conducting air from the external atmosphere into the helical air conduit. 'At. the opposite ends of the combustion chambers from where the burners are located, outlets 78 are provided which lead to the exhaust fans 7 9 for carrying oft the products of combustion.

In the operation of the tunnel kiln, which has been described as representative of kilns embodying my invention. the ware which is to be fired is loaded onto kiln cars in suitable ontainers, care being taken that none proects beyond the kiln car or will become displaced during the passage of the car through thekiln. The cars thus loaded are run into the kiln, from the end A, as cars of fired ware are withdrawn from the opposite end. These cars butt closely against each'other, as shown in Fig. 3, so that the four diagonal flues'in the car at the end C of the kiln, and in each successive car thereafter, will, in conjunction with the car next to it, connect the set of four lines in the kiln wall 2l opposite to it with the next set of four lines in the opposite wall 20. There are thus formed four essentially continuous fines passing around the heating and combustion chambers in a sub stantially helical path. Air drawn in through the openings 61 passes upward through the first four verticalconduits 41, across through the first four transverse flucs 43 in the top of the kiln, downward through the first four vertical conduits 42, then through the horizontal conduits into the obliquely disposed passages 52 in the kiln cars; thence into the four vertical conduits 41 beyond those through which it entered the kiln originally, and thus continuously throughout the length of the tunnel kiln until it has reached the opposite end where it is drawn out by the exhaust fan. The other exhaust fans likewise draw air into the combustion chambers and withdraw products of combustion therefrom, in accordance with the locations of the various valves, as is determined by the nature of the ware to be treated and the heat curve desired.

The air which is drawn through the helical lines in the walls of the cooling zone BC is heated by the residual heat contained in the Ware which has been fired and when drawn into the combustion chambers absorbs but little heat from the flames in being brought up to the temperature of nit-ion. That portion of the air which continues on tl: ugh the helical lines is heated up as it passes through the vertical fines in contact with the combustion chambers and gives otl'this heat to the heating chamber as it passes through the transverse conduits in the roof and through the tops of the kiln cars, thus bringing these portions of the heating chamber to a temperature closely approaching that of the side portions of the heating chamber which are heated directly by radiation from the combustion chambers themselves.

It will be apparent to-those skilled in the art that my invention may be adapted in various other ways and'to the construction of high and of low temperature tunnel kilns, but it is to be understood that such adaptations and modifications are to be considered as broadly comprehended and included by the tollowing claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A tunnel kiln comprising outer walls defining a kiln chamber for conveying ware therethrough,.a combustion chamber within the kiln arranged longitudinally thereof, means providing an air conduit adjacent the i ,eeaa in combustion chamber, and means for positive I circulating air through said conduit to absorb heat from the'combustion chamber and transfer it indirectly to the ware.

2. A tunnel kiln comprising side and connccting walls spaced apart for the passage of ware therethrough, a mbustion chamber arranged within the kiln to heat the ware, structural means defining a heat conducting conduit having a refractory Wall portion exposed to the heat of the combustion chamber and another wall portion for transmitting heat directly to the wars, and means to circulate air through said conduit. I

3. A tunnel kiln comprising kiln walls defining a passage for conveying ware therethrough, a combustion chamber arranged longitudinally within the kiln to ware, structural means defining an air conduit on the side of the combustion chamber opposite from the wars, said conduit having an extended Wall from which heat may be radiated directly to the ware, and means to circulate air positively through said conduit.

4. A tunnel kiln comprising kiln walls defining a passage for the conveying of wars therethrough, a combustion chamber disposed longitudinally within said kiln, structural means defining a continuous as sage through which ainrnay circulate allernately adjacent a muitle Wall and the wars for transferring, heat indirectly thereto, and means for effecting a positive circulation of air through said passage. I

A tunnel kiln comprising outer kiln walls arranged for the passage of ware therethrough, a combustion chamber disposed longitudinally within the kiln and separated from said outer walls, means, in-

eluding partitions between the outer kiln Wall and the combustion chamber, forming an air conduit for transferring heat from the rear of the combustion chamber indirectly to the ware, means for drawing air through said air conduit, and means for supplying fuel to the combustion chamber and for heat the withdrawingproducts of combustion therefrom.

6. A tunnel kiln comprising inner side and connecting walls spaced apart to form a kiln chamber for the passage of ware, a combustion chamber having front and rear refractory walls, the front wall being in common with a portion of one of said kiln chamber walls for transmitting heat directly tothe'kiln chamber, and means includingouter walls cooperating with said rear wall to form a hot air conduit adjacent the combustion chamber and with one oi" said inner kiln walls to form a continuation of said conduit for transmitting heat indi rectly to the ware through the inner kiln wall.

tion, side walls and a top Wall constructed and arranged for the passage of ware therethrough, a longitudinal combustion chain ber Within the kiln and spaced from its walls for radiating heat to the ware and rearwardly to an air space and structural means including a thin wall adjacent the ware which cooperate with said kiln structure to form an air chamber communicating with said air space for conveying heat therefrom to said wall and indirectly thereby to the ware.

8. A tunnel kiln comprising walls constr lcted for the passage of Ware theretl ro'ugh, a longitudinal combustion chamber within said kiln for heating the ware, structural means defining an air conduit surrounding the ware-passage and combustion chamber, and means for positively circulating air through said conduit to transfer heat from the combustion chamber to the wane.

9. A tunnel kiln comprising walls torming a longitudinal heating chamber for the passage of ware therethrough, a combustion chamber disposed longitudinally of the kiln, and structural means defining a continuous air conduit extending transversely around said heating and combustion chambers in 'a substantially helical path.

10. A tunnel kiln comprising walls defining a kiln chamber for the passage of \vare therethrougl'i, a combustion niuttle within the kiln for heating the Ware, structural means defining an air passage substantially surrounding the cooling zone of the kiln and means for positively circulating air therethrough.

11. A tunnel kiln comprising walls defining a kiln chamber for the passage of \vare therethrough and having a continuous helical air conduit surrounding the \vare chamher in the cooling zone of the kiln or absorbing heat from the Ware, a combustion muffie disposed longitudinally of the kiln in the heating zone, means for introducing fuel to the combustion chamber aud tor withdrawing the products of combustion therefrom, and means I01 circulating air through said continuous conduit. i

12. A tunnel kiln comprising walls defininga kiln chamber for the passa e ofwvare therethrough, a combustion chain er within the heating zone of said kiln, structural means defining a conduit in the cooling zone of the kiln, means for positively circulating air through said conduit, and regulatable means for admitting air from the external atmosphere to separated portions of the conduit.

13. A tunnel kiln comprising Walls spaced apart for the passage of Ware therethrough, a combustion chamber longitudinally disposed Within the heating zone of the kiln, an air conduit Within the cooling zone of the kiln having a valve controlled inlet opening into said chamber, and means for drawing air into the combustion chamber or bypassing it to a separate exit.

14. A tunnel kiln comprising walls spaced apart for the passage of ware theretl'irough, a combustion chamber disposed longitudinally within the kiln, structural means comprising inner walls forming a kiln chamber and a substantially helical air conduit around said kiln chaniccr and adjacent said combustion chamber to transfer heat from the latter to the former, and regulatable means for in' troducing air into said conduit to vary the temperature thereof.

15. A tunnel kiln comprising walls defining a kiln chamber for the passage of ware thercthrough, structural means forming a conduit for circulating air around said kiln chamber in the cooling zone thereof, a combustion muille disposed longitudinally of the kiln, said air conduit having a passage coniniuni *ating with the nufile chamber, means for drawing air through said air conduit and into the muffle chamber and for withdrawing products of combustion from the latter, and regulatable means for admitting air from the external atmosphere to spaced portions of said conduit.

, 16. A tunnel 1' ln comprising outer walls defining a passage for conveying ware therethrough. a combustion chamber arranged longitudinally Within the kiln chamber, means forming an air conduit adjacent the kiln chamber walls in one part and adjacent the combustion chamber inanother part, means for regulatably drawing air through said conduit to transfer heat from the combustion chamber to the kiln chamber, and means providing regulatable inlet openings from said air conduit to the combustion chamber at separated points.

17. A tunnel kiln comprising walls forming a passage for conveying ware therethrough, a combustion chamber arranged longitudinally Within the kiln for heating the ware, a series of ware-conveying cars within said passage, each car having a 'refractory body provided with transverse conduits therethrough, structural means defining air conduits Within the kiln having openings communicating with said transverse conduits, and means for positively circulating air through said conduits.

18. A tunnel kiln comprising Walls forming a passage for conveying Ware therethrough, a mutlle longitudinally disposed within said kiln for heating the Ware, a series of ware-conveying cars within the passage, each car having a refractory body provided with a transverse passage there through, structural means forming a series of air conduits passing adjacent the combustion chamber for absorbing heat therefrom, said conduits having openings communicstiiig with the trsiisver e eessas'es in the cars, and means for posii "'ely circ ing sir through said passages conduit 19. A tunnel kiln comprising Wells defining a kiln chamber for she conveyance of were therethrough, a combustion chamber dis osed longitudinally of thelzi n, means, inc uding a series of wereconveying cars having refractory bodies provided with horizontal transverse passages th rethrough, forming a substantially helical conduit surrounding the kl chamber, means for positively circule'aing air through said conduii.

A tunnel kiln comprising foundry tion outer side walls a too well, tory members Within she Min forming a combs-scion chamber spsoed from outer kiln wells and located on each s as or" t is were passage, intermediate pa rations tending from the outer members or the 00311 bustion chambers 10 the outer side walls and iorming upright sir fines, an inner refractory well beneath spaced. from said,"

top Willi and partitions coeci'ii b izherewirh To form conduits which coimeci; "'lie iipgper ends of the upright dues, and tinesiis forming With said does a continuous passage for the circulation of air to transfer ll ili from the rear of the comhusiion chamber th inner refractory well and. indirectly there through to the Will 21. A tunnel. kiln comprising outer iv-ell definingn pass 'e for conveying were there throu flwllfiil chamber i scent a side wail of the "mood therefrom, a Wereconveying oer Within the kiln having a refractory body thereon and transverse passages therethro'ugh, structural means coop-- erating ith the kiln well and the (Emil o-U9 tion chamber defining air concluills in the vdiets rear of said chamber and providing a communication from she air conduits to the passages in the car body, further structural means providing a continuation of said air condui, and having a refractory well through which host may be radiated to the were Within the kiln for circulating eir positively through said coeduiis and car passage.

A; tunnel kiln comprising a foundation, outer side walls and a roof, interme- Walls cooperating with .said outer side walis to form upright air does, a refractory well spec-ed from the roof wall and coo erotiiig therewith to form :1 transverse air flue connecting the upright fines, refractory Wells spaced from the intermediate side walls and cooperating therewith and. with the top refractory We ll and the founda'eion Wells of the kiln so form a longitudinal combustion chamber on each side of e kiln chem her, which transfers heat directly through its from Well so the were and through its rear Wall to the upright fines, e kiln car within the kiln chamber comprising a refractory body having oblique transverse chamber, and means passages therethroogh, the foundation wells connecting the through a tunn l kiln comprising a our platform and 2 "r2 ory top thereon llli' ing diagonally ispcsedi horizontal conduits therethroiigh, substantially as described.

Signed at lVoroester, Massachusetts, this 27th day of Jar, 1921.

THRE'LARSSON. 

